The present invention relates generally to AC powered light devices, and more particularly to an AC powered organic light emitting diode (OLED) device.
Organic electroluminescent devices, such as organic light emitting diodes (OLEDs), are currently used for display applications and are planned for use in general lighting applications. An OLED device includes one or more organic light emitting layers disposed between two electrodes, e.g., a cathode and a light transmissive anode, formed on a light transmissive substrate. The organic light emitting layer emits light upon application of a voltage across the anode and cathode. Upon the application of a voltage from a voltage source, electrons are directly injected into the organic layer from the cathode, and holes are directly injected into the organic layer from the anode. The electrons and the holes travel through the organic layer until they recombine at a luminescent center. This recombination process results in the emission of a photon, i.e., light.
Large area OLED devices typically combine many individual OLED devices on a single substrate or a combination of substrates with multiple individual OLED devices on each substrate. Applications for large area OLED devices include lighting. For most of these applications, alternating current (AC) power is most readily available. However, OLEDs have rectifying current/voltage characteristics and so are typically operated with direct current (DC) power wired with the correct polarity for light emission. In these applications, AC power is converted to DC power to operate the large area OLEDs.
In many signage applications, the sign or display system comprises a light source, and a covering sheet overlying the light source to define the image or lettering desired. The covering sheet is partly opaque and partly transparent. Light from the light source is transmitted through the transparent regions of the covering sheet but not through the opaque regions. Thus, typically, a covering sheet is required to define the image or lettering desired.
It would be an advantage to provide an OLED system, such as a large area OLED, where the individual OLED devices of an array of OLED devices could be powered directly by AC power. Such a system does not require AC to DC power conversion and conditioning, and thus lowers the cost for the OLED system.
It would also be an advantage to provide an OLED system, such as a large; area OLED, that did not require a covering sheet to define an image or lettering, and that required only a number of individual OLED devices to define the image or lettering.
In accordance with one aspect of the present invention, there is provided a light emitting device comprising at least one OLED module, and an AC power source electrically connected to and providing an AC voltage to the at least one OLED module.
In accordance with another aspect of the present invention, there is provided a light emitting device comprising a plurality of organic light emitting diode (OLED) modules electrically connected in series, and an alternating current (AC) power source electrically connected to and providing an AC voltage to the plurality of OLED modules.
In accordance with another aspect of the present invention, there is provided a method of operating the light emitting devices described above, the method comprising providing an AC square waveform voltage to the first and second conducting layers.
In accordance with another aspect of the present invention, there is provided a method of making a light emitting device comprising providing a substrate, forming a plurality of OLED series groups on the substrate, each OLED series group comprising a plurality of OLED modules, the OLED modules of each OLED series group electrically connected in series, wherein the OLED modules may emit light upon application of an AC voltage.
In accordance with another aspect of the present invention, there is provided a method of making a light emitting device comprising providing a substrate, forming a first conducting material over the substrate, forming an organic light emitting material over at least part of the first electrode material, forming a second conducting material over at least part of the organic light emitting material, and patterning the first conducting material, organic light emitting material, and second conducting material to form a plurality of organic light emitting diode (OLED) modules, each OLED module having a first electrode formed from the patterned first conducting material, a light emitting layer formed from the organic light emitting material, and a second electrode formed from the patterned second conducting material, the first and second electrodes of respective OLED modules electrically connected to electrically connect the OLED modules in series.
In accordance with another aspect of the present invention, there is provided a display comprising a plurality of OLED modules arranged to spell out a letter or depict an image.
In accordance with another aspect of the present invention, there is provided a method of making a display comprising providing a substrate, and arranging a plurality of OLED modules to spell out a letter or depict an image.